but Oblivion benefits from a more user friendly interface as well as fully voiced dialog, better graphics and combat mechanics.

I would say that Oblivion suffers from being fully voiced. I'm not against voice acting in games, but the voice acting in Oblivion was bad. You had only a handful of voice actors, so you constantly heard the same voice, many generic dialogues could switch in tone (when talking to a beggar he could suddenly turn all noble in his way of speaking depending on what dialogue options you picked). It all served as a major immersion breaker for me.